If she were to "theoretically" be bred, she would very likely produce deaf puppies. Rather a more important consideration than their colour, don't you think?
If you actually read the information presented at the beginning of this thread by Marimat - and that is scientific fact, not a lay opinion - it would be patently obvious why white boxers should never be bred. Put simply, whether they are themselves deaf or not, their offspring very likely would be whether coloured or not. As Dr Strain stated "Breeding these dogs back into the boxer gene pool will very likely increase the overall incidence of deafness in ALL boxers (white or otherwise)." THAT is "what the harm in it" is.
Deliberately breeding a known defect into a dog breed is irresponsible in the extreme.
Frankly, I find it incredible that you are putting this issue in terms of a dog having a "right to breed". Dogs don't have rights to breed - they have (or should have) the right to be treated as loved pets and companions by owners who have put the best interests of their pet as the primary consideration. Well, being bred is not in the best interests of anyone's pet. It's a significant risk to their health.
What I think you really mean is that YOU just want to breed your dog. And ethics or the good of the breed be damned, you imagine you have a right to breed her. Well, breeding isn't a right, it's a responsibility.
95% of boxers, of any colour, should never be bred. They're the lucky ones. Your white bitch should be one of them.